1. Field of the Invention
The present invention relates generally to semiconductor devices and particularly to semiconductor devices that can be packaged with enhanced anti-bendability.
2. Description of the Background Art
In recent years, semiconductor devices have been further reduced in size and further increased in density to meet a demand for smaller and lighter mobile phones, mobile information equipment and other similar electronics and electronic equipment. To meet this demand there has been proposed bare-chip packaging, a technique applied in mounting an LSI chip directly on a printed circuit board.
Reference will now be made to FIGS. 5A and 5B to describe bare-chip packaging. As a bare chip, an LSI chip 7 has thereon an electrode on which ball-bonding is for example employed to provide a metal bump 14 thereon to serve as an external connection electrode. With reference to FIG. 5A, with metal bump 14 aligned with an electrode 10 provided on a printed circuit board 9 to be packaged, LSI chip 7 is packaged on printed circuit board 9 facedown. FIG. 5B shows a complete packaging.
The market for mobile equipment such as mobile phones and PHSs has significantly expanded. As such, technological innovation has been promoted therefor and bare-chip packaging has thus been increasingly adopted. Conventionally, a package is impaired in reliability generally when temperature cycle causes thermal stress and thermal distortion resulting in defects. In addition, mobile equipment carried by a user can disadvantageously bend when it receives external force. Furthermore, disadvantageous bending stress can instantly occur when mobile equipment is dropped. Furthermore, in a process for manufacturing such mobile equipment, bending stress can occur in a printed circuit board while components are packaged. As such, it is also an important condition that mobile equipment have a mechanically reliable structure impervious to bending stress and the like.
Herein, the semiconductor device shown in FIGS. 5A and 5B has main components with their respective Young's moduli, as follows:
LSI chip (Si): approximately 12 to 14×1010 N/m2 
Printed circuit board: approximately 0.5 to 2.5×1010 N/m2 and it can be understood that LSI chip 7 is formed of a material hard to bend as compared with the printed circuit board. As such, when force is exerted on printed circuit board 9 to bend it, LSI chip 7 does not accordingly bends. Thus, stress concentrates at a solder connection connecting printed circuit board 9 and LSI chip 7 together and when the limit of the stress has been reached the solder connection disadvantageously breaks and thus disconnects.
The present invention therefore contemplates a semiconductor device capable of alleviating such a disadvantage as described above when the entirety of a printed circuit board receives force exerted to bend it, and a method of manufacturing the same.